ii8 N. J. Mosquito Extermination Association 



available for drainage work. The cost of maintenance is directly pro- 

 portionate to the initial-cost of the work and dependent on it. Proper- 

 ly installed drainage systems entail low maintenance costs ; drainage 

 poorly planned and poorly executed means rising maintenance. 

 Steady improvements in organization and equipment mean better 

 drainage at lower costs as the work goes on and each year should 

 see decided progress being made in all departments, scientific study 

 and planning, good engineering in the actual construction work, 

 careful and constant inspection are the fundamentals of mosquito 

 control drainage measures and if these are practiced, drainage 

 systems for mosquito control will reach a maximum of efficiency 

 at a minimum cost with a proportionately reduced cost of main- 

 tenance. 



President Rider : The next number on the program is, "Oils 

 and Larvicides Used in Mosquito Control Work, Their Efficiency 

 and Their Practicability," fifteen minutes, by Walter R. B. Delaney, 

 Sanitary Engineer of the Hudson County Mosquito Commission. 



Mr. Walter B. Delaney : The most effective of mosquito con- 

 trol, aside from drainage and filling, is the intelligent and efficient use 

 of oils and larvicides. 



The object to be attained in using oils and larvicides is to des- 

 troy larvae of mosquitoes. To attain their destruction the surface 

 •of the water must be completely and continuously covered with a 

 film of oil, or if a larvicide is used, it must readily mix with water. 



The effects produced by using oils and larvicides in prevent- 

 ing mosquito breeding are : 



When Oil is Used — Larvae cannot penetrate the oil film with their breathing 

 tubes, and therefore drown ; oil appears toxic to tert young larvae, but with 

 older larvae, it is the mechanical action of the oil resting on the surface of 

 the water in an even layer that suffocates the larvae, and not any poisonous 

 effects ; oil reduces surface tension, making it difficult for the larvae to stay 

 at the surface of the water long enough to breath the oil film and obtain air ; 

 mosquitoes do not oviposit on well oiled water surfaces. 



When Larvicide is Used — Larvae are killed by direct contact, and in some 

 cases, the development of ova is retarded, if not entirely prevented. 



Petroleum : The use of oil — petroleum has been known since 

 early in the nineteenth century, but to Dr. L. O. Howard, the Father 

 of Mosquito Campaigns, goes the credit for its first practical appli- 

 cation. 



There are many grades of petroleum on the market that can be 

 used for larval destruction, but the one best grade to use, is a matter 



